Protein Phosphatase 2A (PP2A) Holoenzymes Regulate Death-associated Protein Kinase (DAPK) in Ceramide-induced Anoikis

作者：Ryan C. Widau, Yijun Jin, Shelley A.H. Dixon, Brian E. Wadzinski, Patricia J. Gallagher · 发表于：Journal of Biological Chemistry · 年份：2010 · DOI：10.1074/jbc.m109.085076 · 被引用次数：52 · 研究领域：Protein Kinase Regulation and GTPase Signaling、Protein Tyrosine Phosphatases、Microtubule and mitosis dynamics

The tumor suppressor, death-associated protein kinase (DAPK), is a Ca(2+)/calmodulin-regulated Ser/Thr kinase with an important role in regulating cytoskeletal dynamics. Autophosphorylation within the calmodulin-binding domain at Ser-308 inhibits DAPK catalytic activity. Dephosphorylation of Ser-308 by a previously unknown phosphatase enhances kinase activity and proteasome-mediated degradation of DAPK. In these studies, we identified two holoenzyme forms of protein phosphatase 2A (PP2A), ABalphaC and ABdeltaC, as DAPK-interacting proteins. These phosphatase holoenzymes dephosphorylate DAPK at Ser-308 in vitro and in vivo resulting in enhanced kinase activity of DAPK. The enzymatic activity of PP2A also negatively regulates DAPK levels by enhancing proteasome-mediated degradation of the kinase. Overexpression of wild type DAPK induces cell rounding and detachment in HEK293 cells; however, this effect is not observed following expression of an inactive DAPK S308E mutant. Finally, activation of DAPK by PP2A was found to be required for ceramide-induced anoikis. Together, our results provide a mechanism by which PP2A and DAPK activities control cell adhesion and anoikis.